Fluids such as oil, natural gas and water are obtained from a subterranean geologic formation (a “reservoir”) by drilling a well that penetrates the fluid-bearing formation. Once the well has been drilled to a certain depth the borehole wall must be supported to prevent collapse. Conventional well drilling methods involve the installation of a casing string and cementing between the casing and the borehole to provide support for the borehole structure. After cementing a casing string in place, the drilling to greater depths can commence. After each subsequent casing string is installed, the next drill bit must pass through the inner diameter of the casing. In this manner each change in casing requires a reduction in the borehole diameter. This repeated reduction in the borehole diameter results in a requirement for very large initial borehole diameters to permit a reasonable pipe diameter at the depth where the wellbore penetrates the producing formation. The need for larger boreholes and multiple casing strings results in the use of more time, material and expense than if a uniform size borehole could be drilled from the surface to the producing formation.
Various methods have been developed to stabilize or complete uncased boreholes. U.S. Pat. No. 5,348,095 to Worrall et al. discloses a method involving the radial expansion of a casing string to a configuration with a larger diameter. Very large forces are needed to impart the radial deformation desired in this method. In an effort to decrease the forces needed to expand the casing string, methods that involve expanding a liner with longitudinal slots cut into it have been proposed (U.S. Pat. Nos. 5,366,012 and 5,667,011). These methods involve the radial deformation of the slotted liner into a configuration having an increased diameter by running an expansion mandrel through the slotted liner. Such methods still require significant amounts of force to be applied throughout the entire length of the slotted liner.
In some drilling operations, another problem encountered is the loss of drilling fluids into subterranean zones. The loss of drilling fluids usually leads to increased expenses but also can result in a borehole collapse and a costly “fishing” job to recover the drill string or other tools that were in the well. Various additives, e.g. cottonseed hulls or synthetic fibers, are commonly used within the drilling fluids to help seal off loss circulation zones.
Furthermore, once a well is put in production an influx of sand from the producing formation can lead to undesired fill within the wellbore and can damage valves and other production related equipment. There have been many attempted methods for controlling sand. For example, some wells utilize sand screens to prevent or restrict the inflow of sand and other particulate matter from the formation into the production tubing. The annulus formed between the sand screen and the wellbore wall is packed with a gravel material in a process called a gravel pack.
The present invention is directed to overcoming, or at least reducing the effects of one or more of the problems set forth above, and can be useful in other applications as well.